Since the initial descriptions of psychotic syndromes, psychiatrists showed the importance of identifying aberrant thought organization through the language in order to predict clinical outcomes, such as cognitive loss linked to Schizophrenia (initially named “dementia praecox”). The description and qualification of formal thought disorder remained complex and subjective until the advent of computational tools that aim to quantify these symptoms on free speech. One strategy based on graph theory studied non-semantic structural features by quantifying spontaneous word trajectory topology. Initially, it was possible to characterize that dream reports from patients with a schizophrenia diagnosis were represented by less connected graphs, and these aspects of language were correlated with negative symptoms. These markers were able to automatically identify reports from patients with schizophrenia diagnosis with more than 90%accuracy, even during the first clinical interview at the first psychotic episode. As these markers appear early on, it was important to understand its typical development and cognitive correlates. First, collecting memory reports at public schools in Brazil, we were able to identify a correlation of graph connectedness with IQ and theory of mind performances, and an independent correlation with reading acquisition. More, studying memory reports from more than 200 subjects with different age (0 to 60 years old) and educational level (0 to 20 years of education), we could identify in typical subjects an asymptotic development of language graph attributes (as lexical diversity, connectedness and graph length increased, short-range recurrence decreased). These changes over time depended more on education than age, and the stabilization of connectedness (language marker of schizophrenia), required at least 13 years of education, or high-school level. Importantly, for atypical development (subjects that presented psychotic symptoms), there was no correlation of graph attributes with age or education, presenting at adulthood a children-like speech structure. Typical subject increased language connectedness over school years, but subjects with psychosis seem to be resistant to formal education, failing to mature in complexity and remaining to a near-random language structure. These results point to feasibility to search for early markers of cognitive risk in naturalistic settings such as the school environment, enabling early identification and intervention to mitigate cognitive damages.
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